For the treatment of a disorder known as pulpitis, the diseased pulpa is removed mechanically from the root canal and the root canal is cleaned and drilled out, filled with an elastic-plastic element or with a different filling material and then sealed. An ideal root canal filling material should not irritate the periapical tissue, should close the root canals sealingly laterally and vertically, its volume should remain stable and it should not shrink in the root canal. For the prior art, see, for example, Friedman et al. In J. Dent. Res., 54 (1975) 921-925, Briseno in Philipp J., 2, 90, 65-73 and U.S. Pat. No. 4,632,977. As root canal filling materials, Briseno describes inter alia semi-rigid cements based on synthetic resin, zinc oxide eugenol, calcium hydroxide or glass ionomer. U.S. Pat. No. 4,632,977 proposes filling materials based on tans-polyisoprene, for example based on gutta-percha or balata. Gutta-percha points are commercially available, the standard composition thereof being 20% by weight of gutta-percha as matrix, from 60 to 75% by weight of zinc oxide as filler, from 1 to 17% by weight of heavy metal sulphates as X-ray contrast agent and from 3 to 4% by weight of waxes and resins as softener. That known filling material is inert in the root canal and accordingly does not react with body tissue.
Such gutta-percha points are usually introduced into the root canal by so-called vertical or lateral condensation.
In vertical condensation, a gutta-percha point is inserted into the root canal and its position in the canal is monitored by means of X-ray imaging. A sealer is then introduced into the canal, together with the gutta-percha, and the root canal is completely filled by alternate insertion and condensation of the thermoplastic gutta-percha in a number of working operations. Heated and softened gutta-percha can also be inserted into the root canal on a carrier point. Finally, molten gutta-percha can be inserted using a gutta-percha gun.
That method has the disadvantage, however, that the heat may denature the tissue surrounding the tooth and thus damage it. Moreover, the gutta-percha may be oxidized and/or degraded or cracked during heating. In particular, repeated hating of gutta-percha may result in degrading and thus ageing of the material.
In lateral condensation, gutta-percha points are introduced in succession into a root canal and are pressed against the sides of the root canal until the root canal is completely full. A disadvantage of that method is that the gutta-percha points must be pressed into the root canal with a certain application of force, which may result in fracture of the teeth. In addition, in vertical condensation, there is the risk of pressing too hard, as a result of which gutta-percha points may be pushed into the periapical tissue, which may lead to irritation or even to inflammation there.
The film thickness of the sealer is also important. In lateral condensation it is not, however, possible to set this precisely.